High frequency spark discharge system



United States Patent [72] Inventor Jerry L. Nolting Fishkil], New York [211 App]. No. 763,681 [22] Filed Sept. 30, 1968 [45] Patented Dec. 8, 1970 [73] Assignee Texaco Inc.

New York, New York a corporation of Delaware [54] HIGH FREQUENCY SPARK DISCHARGE SYSTEM 9 Claims, 1 Drawing Fig.

[52] US. Cl. 123/148, 315/209 [5]] Int. Cl. F02p 3/06 [50] Field ofSearch l23/148(DC) ReferencesCited UNITED STATES PATENTS 3,357,415 12/1967 l-Iuntzinger..... ....l23/l48(E)UX 3,448,732 6/1969 Weiss ..l23/l48(E)UX Primary Examiner-Laurence M. Goodridge Attorneys-K. E. Kavanagh and Thomas H. Whaley ABSTRACT: An ignition system of the type applicable to internal combustion engines in general. The system employs a silicon controlled rectifier having a simplified oscillatory circuit to provide a high frequency spark discharge.

PATENTED nu: BISYO, 3.545419 BACKGROUND OF THE INVENTION 1. Field of the Invention w I This application pertains to an electronic system in general, and more specifically to one that relates to an ignition system for internal combustionengines. It is particularlypertincnt to the field of silicon controlled rectifier type ignition systems.

2. Description of the Prior Art Heretofore, there have been various arrangements suggested for employing solid state electronic elements in ignition systems. Furthermore such systems have included, the use of silicon controlled rectifiers. However, they have had the drawback of providing only a single spark discharge for a given ignition; except where there was included a complicated control circuit for causing aplurality of discharges during one ignition spark. On the other hand the applicants invention provides a simple silicon controlled rectifier system that produces acontrolled, relatively high frequency discharge. Therefore a multiple spark signal may be applied for a given ignition cycle. Also, the frequency of such'spark discharges may be regulated in a desirable range such as l-l0,000 cycles per second Hertz,

SUMMARY OF THE INVENTION Briefly, the invention concerns a high frequency spark I path for said spark discharge current. Finally, the system also 7 comprises second circuitmeans including an impedancefor connecting said gate to said anode as well as short-circuiting means controlled by said points for holding the potential at said gate equal to that at said cathode.

. BRIEF DESCRIPTION OF THE DRAWING The drawing figure shows a circuit diagram illustrating a preferred embodiment of the system according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The art of employing silicon controlled rectifiers with elec: tronic systems to be used for creating spark discharge in connection with internal combustion engines, is quite well developed. However, such prior arrangements have all been concerned with ensuring that there will be only a single discharge through the silicon controlled rectifier. This was done for various reasons including a fear that the SCR would be burned out. Furthermore, even where it has been considered that a multiple spark discharge might bebeneficial, there was provided a system that employed additional circuit elements for controlling gate signals to the SCR. Such additional elements add complications and increase the expense.

Referring to the single figure of the drawing, it will be noted that there is a silicon controlled rectifier 11. It has included among the elements thereof, an anode 12, a cathode l3, and a gate 14. This SCR 11 is connected across the output of a rectifier bridge 17 that has one pair of the diagonals thereof, conwould .be connected to a plus terminal23 and to the ground connection illustrated.

The rectifier bridge 17 supplies a DC potential across the SCR 11 and also across, i.e. in parallel with, the combination .of a capacitor 25 in series with a primary coil 26.

The coil26 is part of an internal combustion engine ignition system and when the SCR 1] conducts it will short circuit the DC supply as well as discharge the capacitor 25 through the coil 26. The discharge current from the capacitor 25 flows over a short circuit path that includes the conducting SCR 11. Such discharge current provides a magnetic field change at the spark coil 26 and this induces a high voltage spark signal in a secondary winding 27. Winding 27 may be connected to a distributor (not shown) for directing the spark signals to individual-sparkplugs of an internal combustion engine..This is indicated by the caption spark DC It will be observed that there is a switch 30 that is connected to the gate [4 of the SCR 11, as well as to a common or ground circuit wire 31. The cathode 13 of SCR 11 is also connected to the common circuit 31.

. and thus short circuit the series connected capacitor 25-coil 26 at the same time as it short circuits the output of a DC charging potential, e.g. the bridge 17. Another short circuit is that related to the points, or switch 30. When the latter short circuit (which is controlled by the points) is closed, it will hold the potential at the gate 14 equal to. the potential at the cathode 13 of the SCR 11, as has just been mentioned. The

latter short circuit means therefore determines the off time for spark discharge signals.

It will be observed that there is a variable resistor 34 that is connected in series with a rectifier 3.5. Both are connected across the SCR 11 between the anode 12 and the gate 14. It may be noted also that there is a common circuit point A which is formed by a common circuit wire 36. Wire 36 connects one side of the capacitor 25 to the end of the resistor 34 that connects to the anode 12 of SCR ll. Wire 36 also connects an output diagonal of the bridge 17 to the anode l2 and so to the other two elements also, as just indicated.

The operation of the circuit may be briefly described as follows: when switch 30 is open, a voltage builds upacross the SCR l1 toa sufiiciently high value, e.g. approximately 300 volts. At that time there is sufficient current flow through the resistor 34to the gate 14 so that the SCR 11 will be triggered Consequently, the applicants invention has the real attribute of simplification while also providing stable and adjustable operation so that a desired high frequency spark discharge may be obtained at a predetermined rate e.g. in the range of l- 10K Hertz. I

The applicant is taking the liberty of using the abbreviation into conduction. When the SCR 11 conducts it shorts out the power supply and also discharges capacitor 25 through the ignition coil 26. That action causes voltage at the point A to swing negative and therefore the SCR 11 is turned off, i.e. it stops conducting. When the SCR 11 stops conducting, the power supply that feeds the bridge 17' is no longer short circuited and the oscillator circuit 20 may oscillate once more. Then the voltage output from bridge 17, again builds up to reach the voltage necessary to repeat the foregoing action. Thus, the SCR 11 is again fired and the rest of the cycle described will repeat itself.

By setting the circuit constants at predetermined values, the repetition rate of spark discharge action may be predetermined. One specific example of particular values that have been employed with the illustrated circuit are as listed below.

It may be noted that while the power supply that is employed uses standard elements, it is important that it have the characteristics which were described above in connection with the operation of the system. Consequently the list of specific values will include those for each of a pair of resistors 39 and 40, as well as two resistors 43' and 44 each of which have a capacitor 45 and 46, respectively, connected thereacross. Similarly, the list will include values for diodes 51, 52, 53, and 54 of the bridge 17 plus a diode 55 that is connected across the switch (points) 30.

The aforesaid list of particular values that may be employed to provide a multiple spark repetition rate of about 5,000 cycles per second (Hertz), is as follows:

Transistors 21 and 22 -Type 2Nl74 Transfonner 19 -A Triad No. TY84 Diodes 51-55 and 35 Type A13N2 (G.E.)

SCR l1Type 2N3670 Resistor 34 K 20l( Capacitor 25 0.1 -2 mfd.

Ignition coil 26-standard l2-volt size While the foregoing description of the invention has been made in considerable detail in accordance with-the applicable statutes, this is not to be taken as in any way limiting the invention but merely as being descriptive thereof.

I claim:

1. A high frequency spark discharge system comprising in combination:

an ignition coil;

points for timing initiation of said spark discharge;

a capacitor for discharging through said coil to create spark energy output;

means for connecting a DC power supply to charge said capacitor prior to spark discharge thereof;

a silicon controlled rectifier having an anode, a cathode,

and a gate; first circuit means for connecting said silicon controlled rectifier across said capacitor and ignition coil to provide a discharge path for said multiple spark discharges:

secondcircuit means including an impedance for connecting said gate to said anode in order to determine the repetition rate of said spark discharges; and

short circuit means controlled by said points for holding the potential at said gate equal to that at said cathode for determining off time for spark discharges.

2. A system according to claim 1 wherein said second circuit means impedance is variable to provide adjustment for maximum power in said spark discharges. v

3. A system according to claim 2 wherein said second circuit means impedance includes a resistor.

4. A system according to claim 1 wherein said second circuit means impedance comprises a variable resistor and a rectifier in series.

5. A system according to claim 1 wherein said short circuit means comprises said points directly connected between said gate and said cathode.

'6. A system according to claim 5 wherein said second circuit means impedance is variable to provide adjustment for maximum power in said spark discharges.

7. A system according to claim 6 wherein said second circuit means impedance includes a resistor.

8. A system according to claim 5 wherein said second circuit means impedance comprises a variable resistor and a rectifier in series.

9. A high frequency spark discharge system comprising in combination:

an ignition coil;

points for timing initiation and duration of said spark discharge;

a capacitor for discharging through said coil to create spark energy output;

a DC power supply comprising:

a transformer having an input and an output winding;

a plurality of connections for said input winding;

a pair of transistors;

first circuit means for connecting said transistors to said plurality of connections to form an oscillator;

second circuit means for connecting a low voltage DC power source to said oscillator;

a rectifier bridge; and

third circuit means for connecting one diagonal of said bridge to said transformer output winding;

means for connecting said DC power supply to charge said capacitor prior to spark discharge;

a silicon controlled rectifier having an anode, a cathode,

and a gate; fourth circuit means for connecting said silicon controlled rectifier across said capacitor and ignition coil to provide a discharge path for said multiple spark discharges;

fifth circuit means including a variable resistor in series with a rectifier for connecting said gate to said anode in order to determine the repetition rate of said spark discharges; and

means for directly connecting said points between said gate and said cathode to hold them at the same potential when the points are closed for determining off time for spark discharges. 

